A radio frequency power amplifier is an important component of a transmitting device. Its main technical indicators include output power and efficiency. Based on the prior art and the core principle of the radio frequency power amplifier, the efficiency of the radio frequency power amplifier is low. The radio frequency power amplifier in the prior art usually adopts a multi-stage gain mode. A bias voltage Vcc1 supplies power to the internal logical circuit and bias circuit. A bias voltage Vcc2 supplies power to the internal radio frequency power amplifier. A communication device normally does not need to transmit signals at the maximum power. In order to increase the efficiency on occasions except when the radio frequency power amplifier uses the maximum power to transmit signals, the bias voltage generally adopts a fixed voltage supply and adopts different gain modes according to different power output requirements, for example, a Vmode0 gain mode and a Vmode1 gain mode.
During the implementation of the present invention, the inventor discovers that the prior art has at least the following problem: If the communication device uses the non-maximum power to transmit signals, the power loss of the radio frequency power amplifier is large and the efficiency is low.